The present invention generally relates to a single swing jaw-type of crushing apparatus wherein rocks or other crushable materials are crushed in a crushing chamber formed below a top feed opening between a large stationary jaw and an oscillating swing jaw. The invention more particularly relates to a single swing jaw crusher having a cantilevered swing jaw design for producing purely compressive crushing forces between the jaws.
Single swing jaw-type rock crushers are well-known and have been used for many years. The basic principal of such crushers is to gravity feed rocks or other crushable materials into a crushing chamber situated between two massive jaws, one and only one of which is a swing jaw driven in a rapid oscillatory motion (generally in the range of 300-400 r.p.m.) about an elongated hinge pin. Conventional swing jaw designs differ in that they include cantilevered designs (sometimes referred to as "gooseneck" swing jaws) and straight jaw designs. In both cases, the swing jaw's hinge structure extends all the way across the top of the crusher whereby the crusher's top feed opening through which crushables are fed into the crushing chamber is formed in the region forward of the swing jaw's hinge axis.
A major difficulty with cantilevered swing jaw designs is that the swing jaw's hinge pin is cantilevered inwardly at the top of the crusher, so that the hinge pin and swing jaw structure itself obstruct the feed opening of the crusher. There is a tendency by users to feed rocks into a crusher which are too large for the crusher to handle and which have to be removed from the feed opening or broken up manually. In large capacity machines where oversized rocks typically range from four to ten tons, auxiliary machines, such as large pneumatic jack hammers, must be used for this purpose. Where access through the feed opening is restricted by the swing jaw hinge structure, as in cantilevered swing jaw designs, it is difficult to insert the ends of these devices at angles which will efficiently accomplish their task.
The above disadvantage of cantilevered swing jaw designs are not generally present in straight swing jaw crushers, such as the Blake-type and overhead eccentric-type crushers. Such crushers have a swing jaw extending in a straight line at a downward angle from its overhead full length hinge. Unlike the cantilevered jaw design, their jaw hinge is generally situated more toward the back of the crusher and therefore the hinge structure does not create a substantial obstruction at the feed opening.
However, there are known and significant disadvantages with straight jaw designs. In the Blake-type crusher, which has a toggle drive at the bottom of the jaw, the motion of the swing jaw forces rock upward, causing it to rub against the jaws and to rapidly wear down the jaw plates; there is also essentially no motion of the jaw at the top of the crushing chamber. In the overhead eccentric-type of crusher, wherein the jaw is driven at its top end by an eccentric bearing, the moving jaw forces rock both up and down with similar results. With the cantilevered swing jaw design, the hinge axis for the swing jaw lies on a plane bisecting the crushing chamber so that a straight line and purely compressive crushing force is produced. This substantially reduces jaw plate wear, and generally permits the swing jaw to operate at more strokes per minute for greater capacity and to do so with less power consumption. Thus, despite the fact that the hinge pin of the inwardly cantilevered swing jaw limits the size of the feed opening to an area forward of the jaw's hinge axis, the cantilevered design provides significant advantages which have led to their widespread use.
A single swing jaw crusher of the above described cantilevered construction is shown in U.S. Pat. No. 4,398,674, to George S. Dremann, wherein it can be seen that the feed opening forward of the swing jaw's hinge pin would generally make the removal of oversized material from the crushing chamber very difficult.
The present invention provides a single swing jaw rock crushing apparatus which has a cantilevered swing jaw design such as shown in the Dremann patent (that is, a single swing jaw crusher with its swing jaw hinge axis over the crushing chamber), but which overcomes the problem encountered by prior cantilevered jaw designs, that of having a restricted feed opening. In the present invention, an enlarged feed opening is provided without sacrificing the advantages of the cantilevered jaw design, namely, extended jaw plate wear, greater capacity, and lower power consumption. The present invention also provides a cantilevered single swing jaw crusher wherein the feed opening can more readily be accessed by percussive devices for breaking up oversized rock, and wherein the cantilevered swing jaw is comparatively easy to manufacture and assemble with a proper jaw angle.